Nope, that doesn't follow.
The last several decades have seen a gradually accelerating series of warnings from climate scientists, from "climate change is becoming a real problem" to "it's a real problem that we really need to address SOON" to "if we don't address it in the next twenty years or so, it will become irreversible", to "if we don't address it in the next ten years or so, it will become irreversible", to "shit, it MIGHT be becoming irreversible now, we really need to do it NOW!", to the current situation where some scientists are saying it's irreversible (though some still aren't).
All the while, the idiots who are determined to ignore it go on ignoring it, and because there's so many of them governments carrying on with woefully insufficient policies in order to win their votes. And you think that's the fault of people telling them it's irreversible? If telling them it's NOT irreversible would be so much more effective, how come it had so little effect on them when it ACTUALLY wasn't irreversible and people told them that because it was the truth?
Then there's the fact that saying a certain level of warming is irreversible doesn't mean that we should do nothing to stop it getting even worse. If 1.5 degrees is irreversible then that's going to cause severe problems that hugely impact upon the way future societies operate and the likely quality of life of children born now. That doesn't mean that if we don't take action to LIMIT it to that, and allow it to get to 2 or 3 degrees instead, the results won't be catastophically worse.
Stop looking for reasons to let people of the hook. Climate reality is not going to do that, it is what it is. People have had all the time in the world to face it and mostly chosen not to, despite every different level of gentle persuasion through to forceful urgency through to fatalism in the messaging. If they insist on digging their own graves (and our children's with them) then it's nobody's fault but their own.